Agaitas and discarding cards at random

How do we discard cards at random if Agaitas is holding my prey's cards in front of me, as if in my hand? It's easier when people aren't using sleeves, but it gets more difficult when it's obvious which card is whose. Should we resort to a D8, or something?

Agaitas, the Scholar of Antiquities

Sabbat: When you play a card, you may draw its replacement from your prey's library instead of your own. Put the card drawn face-up in front of you. It is still considered to be in your hand, to be played or discarded as normal.

Sudario Refraction

+1 stealth action.
Choose three cards in your ash heap and move them to the top of your library. Then discard three cards at random from your hand (and draw up to your hand size afterward).

"Random" means the choice doesn't depend on the options, and, in our case, that each card gets the same chances of getting picked.
You can use a random number generator (usually called "dice").
Or have a player generate randomness ("shuffle") and pick the top 3 cards.
Or have a player "shuffle", and another player give 3 random numbers (use the dice, or just three numbers out of their head).

The bottom line is: When picking at random, all the cards have the same odds of being chosen.

Pascal wrote:

"Random" means the choice doesn't depend on the options, and, in our case, that each card gets the same chances of getting picked.
You can use a random number generator (usually called "dice").
Or have a player generate randomness ("shuffle") and pick the top 3 cards.
Or have a player "shuffle", and another player give 3 random numbers (use the dice, or just three numbers out of their head).

The bottom line is: When picking at random, all the cards have the same odds of being chosen.

That's what I thought. A good idea, when shuffling and letting others draw the cards due to differently coloured sleeves for example, mightbe using a D8 and re-rolling all eights. Cheers!